screen is stuck on loading maps

Hey, I downloaded open source maps for my garmin 810. I loaded them on my 16GB SD card. However, when I insert my card, the screen is stuck on “loading maps.” I have no idea what to do. I followed the directions step by step according to this article. https://www.dcrainmaker.com/2013/05/download-garmin-705800810.html#comment-1825136

Any ideas on what to do???